GB574956A - Improvements in or relating to the manufacture of synthetic linear polyamide yarn - Google Patents

Abstract

Synthetic linear polyamide yarn having high tenacity is obtained by melt spinning at a speed in excess of 3000 feet per minute a synthetic linear polyamide comprising 85-98 per cent of a polyamide having a quench index of 25 mils or less, interpolymerized with 15-1 per cent of a modifying polyamide which raises the quench index by at least 2 mils. The quench index is measured by filling a wedge-shaped sheet-aluminium mould of specified dimensions with the solid polymer; placing in a glass tube and melting under vacuum; removing from the tube and quenching in water at 0 DEG C.; dissolving the aluminium mould so as to leave a wedge of the solid polymer which is clear at the tip of the wedge and for some distance from the tip because of rapid quenching; and measuring the thickness of the wedge at the line of demarcation between the clear and cloudy or opaque portions. The interpolymerizing may be effected not only by heating together in the molten state the two polyamides which are to be polymerized, but also by heating together the monomeric polyamide-forming ingredients and interpolymerizing by well-known methods. The amount of heating involved in the melt spinning of a mechanical mixture of two polyamides is sufficient to produce the required interpolymerization. Polyhexamethylene adipamide may be modified with polyhexamethylene sebacamide. Polyamides having a relative viscosity of less than 20, as determined by measuring the viscosity of a solution containing 8.4 per cent of the polymer in formic acid of 90 per cent strength and the viscosity of this solvent, are preferred. Other polyamides of low-quench indices are polyethylene sebacamide and polyhexamethylene pimelamide. Other modifying polyamides are those from hexamethylene diamine and azelaic acid; 12 - aminostearic acid; decamethylene diamine and sebacic acid; amino capronitrile; piperazinium sebacate; tetramethylene diammonium adipate; caprolactam; decamethylene diammonium 1 : 4-cyclohexane-bis - e - sulphonamido - caproate; ortho - xylyl diammonium adipate; and many others. Polyamide-forming constituents which may be used as modifying agents with a diamine such as hexamethylene diamine are terephthalic acid, p-phenylene diacetic acid, and glutaric acid. Polyamide-forming constituents which may be used as modifying agents with a dibasic acid such as adipic acid are ethylene diamine, N1 : N1-dimethyl hexamethylene diamine and decamethylene diamine. In an example, hexamethylene diammonium adipate is interpolymerized with a small proportion of hexamethylene diammonium sebacate in presence of acetic acid as viscosity stabilizer. The interpolyamide is melt-spun at 2500 to 4500 feet per minute into air and the filaments obtained are cold drawn.